1. Field of the Invention
The invention relates to a pair of edging rolls for edging the flange edges of symmetrical steel sections, particularly I-girders. Each edging roll has a barrel engaging in the inner contour of the section and guiding the section and two edging paths adjoining the barrel at either side and extending outwardly in a conical shape for the flange edges of the section.
2. Description of the Prior Art
Rolling mill trains having universal roll stands and edging stands cooperating with the latter are particularly suited for rolling symmetrical steel sections, in particular I-girders. The preliminary section is reduced in the universal stands in a number of successive reversing passes, while the free-spreading flanges are shaped in the edging stands in that their flange edges are upset or edged. In so doing, it is known to use edging rolls having a barrel which guides the section and edging paths for the flange edges adjoining both sides of the barrel. These edging paths are formed by conically extending portions of the roll. The cone extends outward, i.e. the edging paths increase in diameter from the barrel outward.
The barrel of the edging roll engages in the outer contour of the section and guides it in that the barrel flanks contact the inner flanks of the flange of the section. A gap should remain between the outer diameter of the barrel and the web of the section to be rolled so that the different circumferential speeds of the outer diameter of the barrel and the penetration paths do not have a negative effect. However, it must be ensured that the play or clearance between the outer diameter of the barrel and the web of the section is not too great. Otherwise, an exact centering of the section would no longer be possible. The section floats in the roll gap and an unacceptable bending of the flanges and web occurs.
In this respect, a particular problem arises with reversing rolls in successive universal passes and edging passes in that the flange of the section to be rolled widens or spreads in the universal passes and in that--when the dimensions of the edging rolls are fixed--it is no longer possible for the barrel of the edging roll to penetrate to a sufficient depth into the inner contour of the section due to the contact of the edging paths at the edges of the flanges. This results in disadvantageously large play or clearance in the region of the web of the section and in the deformations of the section described above. This problem occurs especially at the end of the pass sequence in girder rolling with only one edging stand, since the difference in diameter between the edging path of the edging roll and the outer diameter of the penetration-rolling barrel is too small. A possibility for changing the excessive clearance between the barrel of the edging roll and the web of the rolling section is described in the European Patent 02 94 494. In this patent, the barrel of the edging roll is formed from two eccentrically supported rings which slide freely on an adjustable bearing body. The position of the outer ring can be changed in relation to the center of the web of the section by adjusting eccentric intermediate rings and the gap of the outer diameter of the roll barrel can accordingly be changed.
The disadvantage of the known solution is that the edging roll entails a very high production cost as a consequence of the eccentrics which are supported relative to one another and at the same time has a high anticipated wear. The eccentric adjustment of the barrel comprising two disks also changes the chamber dimensioning of the roll, which is likewise disadvantageous. The previously known solution can also not be installed subsequently in existing roll stands because this would necessitate extensive remodeling.